It is known that print quality can be improved by insertion of a compressible material behind a photopolymer or rubber flexographic plate. Additionally, it is known that press bounce and plate wear may be reduced using a compressible material behind the printing plate. Generally, in these prior art printing plates, the compressible material was adhered to the side of the printing plate base layer away from the printing face. Alternatively, the compressible material was adhered to the printing face side of the plate and an intervening layer of dimensionally stable material, such as mylar or paper, was located between the compressible material and the photocurable material.
Additionally, prior compressible printing plates were not translucent to ultraviolet radiation, and, therefore such plates could not be backexposed. Back exposure allows the floor of the photocurable material to develop more fully and, generally, the printing plates made in this manner are more durable than those developed solely by front exposure.
In the past, attempts have been made to position the photopolymer layer directly on top of the compressible layer of the printing plate without an intervening stabilizing layer. In such cases, a layer of solid photopolymer was laminated onto the compressible layer. However, because of the nature of lamination, strong adhesion between the solid photopolymer and the compressible material remained as a problem.
Additionally, since the solid photopolymer cures upon exposure to ultraviolet light, the uncured photopolymer had to be covered by foil or similar material until it was used. Further, since plates using a solid photopolymer layer were pre-made, the final user could not adjust the depth of the printing face nor the depth of the underlying compressible layer.